A bioactive ingredient in an ethanol extract from the branch bark of cultivated mulberry Husang-32 (Morus multicaulis Perr.) was isolated using a macroporous resin column. The primary component, which was purified by semi-preparative high-performance liquid chromatography diode array detection (HPLC-DAD), was identified as mulberroside A (MA) by liquid chromatograph-mass spectrometer (LC-MS), ¹H and ¹³C nuclear magnetic resonance (NMR) spectra. In total, 4.12 g MA was efficiently extracted from one kilogram of mulberry bark. The enzymatic analysis showed that MA inhibited the generation of dopachrome by affecting the activities of monophenolase and diphenolase of tyrosinase in vitro. This analysis indicated that MA and oxyresveratrol (OR), which is the the aglycone of mulberroside A, exhibited strong inhibition of the monophenolase activity with IC₅₀ values of 1.29 µmol/L and 0.12 µmol/L, respectively. However, the former showed weaker inhibitory activity than the latter for diphenolase. For the monophenolase activity, the inhibitory activity of MA and OR was reversible and showed mixed type 1 inhibition. Additionally, the inhibition constant KI (the inhibition constant of the effectors on tyrosinase) values were 0.385 µmol/L and 0.926 µmol/L, respectively, and the KIS (the inhibition constants of the enzyme-substrate complex) values were 0.177 µmol/L and 0.662 µmol/L, respectively. However, MA showed competitive inhibition of diphenolase activity, and K_I was 4.36 µmol/L. In contrast, OR showed noncompetitive inhibition and K_I = K_IS = 2.95 µmol/L. Taken together, these results provide important information concerning the inhibitory mechanism of MA on melanin synthesis, which is widely used in whitening cosmetics.

Platelets play a pivotal role in atherothrombosis and the antiplatelet agents have been proved to be useful in preventing onset of acute clinical events including myocardial infarction and stroke. Increasing number of natural compounds has been identified to be potential antiplatelet agents. Here we report the antiplatelet effect of glaucocalyxin A (GLA), an ent-diterpenoid that we isolated and purified from the aerial parts of Rabdosia japonica (Burm. f.) var. glaucocalyx (Maxim.) Hara, and investigate the molecular mechanisms by which GLA inhibits platelet activation and thrombus formation. The effect of GLA on platelet activation was measured using platelets freshly isolated from peripheral blood of healthy donors. Results showed that pretreatment of human platelets with lower concentrations of GLA (0.01μg/ml, 0.1μg/ml) significantly inhibited platelet aggregation induced by collagen (P<0.001) and CRP (P<0.01), a synthetic GPVI ligand, but not by ADP and U46619. Accordingly, GLA inhibited collagen-stimulated tyrosine phosphorylation of Syk, LAT, and phospholipase Cγ2, the signaling events in collagen receptor GPⅥ pathway. GLA also inhibited platelet p-selectin secretion and integrin activation by convulxin, a GPVI selective ligand. Additionally, GLA was found to inhibit low-dose thrombin-induced platelet activation. Using a flow chamber device, GLA was found to attenuate platelet adhesion on collagen surfaces in high shear condition. In vivo studies showed that GLA administration increased the time for complete occlusion upon vascular injury in mice, but did not extend tail-bleeding time when mice were administered with relatively lower doses of GLA. Therefore, the present results provide the molecular basis for the inhibition effect of GLA on platelet activation and its in vivo effect on thrombus formation, suggesting that GLA could potentially be developed as an antiplatelet and antithrombotic agent.

Acute lung injury (ALI) results from various factors including uncontrolled pulmonary inflammation, oxidative damage and the over-activated complement with high mortality rates. Jaceosidin was a flavonoid compound with significant anti-complement activity. We aimed to investigate the therapeutic effects of Jaceosidin on ALI induced by lipopolysaccharide (LPS). Mice were orally administrated with Jaceosidin (15, 30 and 60 mg/kg) after LPS challenge. 24 h after LPS challenge, Jaceosidin could significantly decrease the lung wet-to-dry weight (W/D) ratio and the protein concentration in bronchoalveolar lavage fluid (BALF). Jaceosidin could down-regulate the levels of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6) and interleukin-1β (IL-1β), together with up-regulation the levels of interleukin-4 (IL-4) and interleukin-10 (IL-10) in BALF. Jaceosidin could significantly decrease the levels of myeloperoxidase (MPO), cyclooxygenase-2 (COX-2) and nuclear factor-κB (NF-κB), COX-2 mRNA and NF-κB p65 mRNA together with increasing the activity of catalase (CAT). Additionally, Jaceosidin attenuated lung histopathological changes, inhibited the expressions of COX-2 and NF-κB p65 and reduced complement deposition with decreasing the levels of complement 3 (C3) and complement 3c (C3c) in serum. These data suggest that Jaceocidin may dampen the inflammatory response and decrease the levels of complement together with the antioxidant activity following LPS-induced ALI.